Current operative methods for treating spinal deformities, particularly scoliosis, include correction of the curve by some internal fixation device, and fusion of the spine in the corrected state usually accomplished by the placement of bone graft between vertebrae. This is usually accomplished with posterior surgery, although anterior procedures are becoming more popular, as well as combinations of anterior and posterior procedures. Several instrumentation systems are available from various manufacturers to correct and stabilize the spine while fusion occurs. Among them are TSRH(copyright), CD(trademark), CD Hopf(trademark), CD Horizon(trademark), ISOLA(trademark), Moss Miami and Synthes Universal Spine Systems. Nonoperative methods do exist and are used when applicable. These nonoperative methods include bracing and observation.
Juvenile idiopathic scoliosis occurs between the ages of 4 and 10 years. It can resolve spontaneously, respond to nonoperative therapy, or progress until fusion is required. Stapling across long bone physes has long been recognized as a predictable method of treating limb malalignment. Vertebral interbody stapling across the cartilaginous endplates and discs was attempted by Nachlas and Borden in a canine scoliosis model. Early human results in the 1950s were disappointing. Roaf reported limited successful correction of scoliosis by uninstrumented convex hemiepiphysiodesis. His study did not have a uniform patient population by skeletal maturity or scoliosis etiology.
Further shortcomings of current operative methods and devices are numerous. Patients with juvenile scoliosis who undergo curve stabilization with subcutaneous rods would be subject to multiple surgical procedures for lengthening as they grow. Anterior and/or posterior spinal fusion in the skeletally immature patient often results in loss of vertebral body height and girth. Additionally, poor self-image may occur in adolescent patients who are braced for scoliosis. Moreover, curve stabilization with bracing is only successful in approximately 75% of patients. Another problem is that some children, while not currently candidates for a definitive fusion procedure, are likely to need such a procedure in the future. These would include children less than ten years of age, small in stature, premenstrual or riser two or lower, and those not physically able to tolerate the surgery required for a definitive fusion procedure. It would be preferable to eliminate the need for that procedure altogether.
In one embodiment, the staple comprises a plate having a first end and a second end and a top surface and a bottom surface and first and second side surfaces, the surfaces extending between the first end and the second end. The plate defines a bore therethrough between the top surface and the bottom surface with a first pair of prongs connected to the first end. Each of the first pair of prongs has a lower end with a tip and an upper end connected to the first side surface. Additionally, each of the first pair of prongs has an interior surface and an exterior surface extending between the lower end and the upper end. The interior surface and the exterior surface of the upper end of the first pair of prongs are adjacent the bottom surface and the top surface respectively of the plate. A second pair of prongs is connected to the second end, each of the second pair of prongs has a lower end with a tip and an upper end connected to the second side surface. Also, each of the second pair of prongs has an interior surface and an exterior surface extending between the lower end and the upper end. The interior surface and the exterior surface of the upper end of the second pair of prongs is adjacent the bottom surface and the top surface respectively of the plate. At least a portion of the staple is manufactured from a shape memory material. The shape memory material has a first memorized state and a second deformed state. The tips of the first pair of prongs are closer to the tips of the second pair of prongs in the first state than in the second state.
In another embodiment, the staple comprises a bridging portion with a first end and a second end and an upper surface and a lower surface and first and second side surfaces, the surfaces extending between the first end and the second end. The staple has a first prong having a first proximal end and a first distal end, the first prong also has a first inboard surface and a first outboard surface extending between the first proximal end and the first distal end. The staple also has a second prong having a second proximal end and a second distal end, the second prong having a second inboard surface and a second outboard surface extending between the second proximal end and the second distal end. A plurality of notches are integrally formed on the upper surface of the bridging portion, the notches permit more precise seating of the staple. The first proximal end is connected to the first end of the bridging portion, and the second proximal end is connected to the second end of the bridging portion. The first and second inboard surface generally face one another. Additionally, at least a portion of the staple is made from a shape memory material. The shape memory material has a first memorized state and a second deformed state. The first distal end is closer to the second distal end in the first state than in the second state.
In another embodiment, the staple is generally U-shaped with a cross bar defining a central axis extending between a first end and a second end. The staple has a first leg with a first proximal portion and a first distal portion. The first proximal portion is integrally formed with the first end. The first leg defines a first longitudinal axis and the first longitudinal axis is at an angle to the central axis. The staple also has a second leg with a second proximal portion and a second distal portion. The second proximal portion is integrally formed with the second end. The second leg defines a second longitudinal axis with the second longitudinal axis being at an angle to the central axis. The cross bar and the first and second legs each have an inner surface and an outer surface and a pair of side surfaces with the inner surfaces of the first and second legs generally facing one another. Additionally, inner and outer surfaces of the first and second legs each contain a plurality of barbs in a direction transverse to the direction of the first and second longitudinal axis respectively.